This invention relates to a kind of built-up inner floating ceiling for use in an oil storage tank, particularly one suitable for use in a vertical cylindrical oil tank made of steel having a fixed ceiling.
Prior art shows that usually an inner floating ceiling is mounted in an oil tank, in order to reduce the evaporative loss of oil and prevent oil from contamination and degradation. A Chinese Patent CN 88 2 01602 disclosed a kind of built-up floating ceiling. The general structure of an inner floating ceiling is as follows. First, steel plates or aluminium plates are processed into H-shaped members, which are then bolted together to form a skeleton. Next, hard obturated foam plastic of polyaminoester is used to make buoys, which in turn are arranged concentrically on the skeleton to form an inner floating ceiling. The disadvantage of such a ceiling is that the problem of electrostatic prevention still remains unsolved. When such a floating ceiling is mounted in an oil tank, petroleum products tend to carry electrostatic charge of a certain symbol, since transfer of charge usually occurs during flow, filtration, feeding and sloshing of petroleum. That's why electrostatic effects cannot be prevented.
It is therefore the primary object of this invention to provide a built-in inner floating ceiling, which can remove electrostatic effects when used in an oil tank.
According to this invention, the afore-mentioned object can be attained with a built-in inner floating ceiling of which the skeleton is fitted with concentrically arranged plastic buoys containing a certain conductive additive, and a metallic net is mounted under said buoys. Said buoys are pressed from right and left, top and bottom, front and rear, by radial beams of the skeleton, cover plates and said metallic net, and peripheral beams of the skeleton, respectively. Said cover plates are further linked by wires to the top of the oil tank. In such a manner, all electrostatic charges are earthened and thus removed.